Brain Scan Combo Better Finds Seizure Source Before Surgery

What was studied

This study looked at whether magnetoencephalographic source imaging (MSI) adds diagnostic value for finding the brain area where seizures start in people with drug-resistant focal epilepsy. The researchers used data from 101 patients prospectively enrolled in the EPIMAGE study, but this analysis focused on the patients who underwent stereo-EEG (SEEG) and/or epilepsy surgery.

The study compared three imaging tests: MRI, FDG-PET, and MSI. The researchers assessed how well each test, and combinations of tests, identified the SEEG-defined seizure-onset zone or matched the surgical resection zone.

What they found

Using SEEG as the reference, MSI identified additional seizure-onset regions beyond MRI in 55.6% of patients, beyond PET in 29.6%, and beyond combined MRI plus PET in 33.3%. Similar added localizing value was reported when the resection zone was used as the reference.

Using two tests together showed higher estimated detection rates than single tests alone. Estimated detection rates were 73.7% for MRI plus PET, 81.3% for MRI plus MSI, and 79.8% for PET plus MSI. Using all three tests together had the highest estimated detection probability at 85.3%, which was significantly higher than MRI, PET, or MSI alone. Adding MSI to MRI or to PET significantly improved seizure-onset zone detection in the model.

Limits of the evidence

This study found improved localization relative to SEEG and resection zones, but it does not show that adding MSI leads to better seizure outcomes after surgery. The abstract does not give the exact number of patients in the SEEG and surgery subgroup, so the size of the main analysis is unclear. The study only included people with drug-resistant focal epilepsy being evaluated in a presurgical setting, so the results may not apply to all people with epilepsy. Also, the abstract gives limited detail about patient characteristics and how results may differ by epilepsy type or brain location.

For families and caregivers

For families considering epilepsy surgery, this study suggests that adding MSI to MRI and PET may help doctors more completely map where seizures begin, especially in complex cases. That may help with presurgical planning.

Still, this does not mean every patient needs MSI or that it will change treatment for everyone. Families can ask whether MSI is available, whether it might add useful information in their child’s or loved one’s case, and how doctors combine imaging results with EEG and other testing.

What to watch next

Useful next studies would test whether adding MSI changes clinical decisions or improves long-term seizure outcomes, not just agreement with SEEG or resection zones.

Terms in this summary

magnetoencephalographic source imaging (MSI)

A test that uses magnetic signals from brain activity to estimate where seizures may start.

epileptogenic zone

The brain area believed to be responsible for causing seizures.

focal epilepsy

Epilepsy in which seizures start in one part of the brain.

drug-resistant

Seizures that continue despite trying appropriate seizure medicines.

MRI

A brain scan that shows brain structure and can reveal visible abnormalities.

FDG-PET

A scan that shows how parts of the brain use sugar, which can help find abnormal brain areas.

SEEG

A test in which thin electrodes are placed in the brain to record exactly where seizures start.

resection zone

The area of brain tissue removed during epilepsy surgery.